linux-kernel - Re: [PATCH] tpm: fix WARNING: lock held when returning to user space

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Date:   Wed, 11 Dec 2019 19:52:02 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Tadeusz Struk <tadeusz.struk@...el.com>
Cc:     peterz@...radead.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, jgg@...pe.ca, mingo@...hat.com,
        jeffrin@...agiritech.edu.in, linux-integrity@...r.kernel.org,
        will@...nel.org, peterhuewe@....de
Subject: Re: [PATCH] tpm: fix WARNING: lock held when returning to user space

On Tue, Dec 10, 2019 at 01:17:51PM -0800, Tadeusz Struk wrote:
> When an application sends TPM commands in NONBLOCKING mode
> the driver holds chip->tpm_mutex returning from write(),
> which triggers WARNING: lock held when returning to user space!
> To silence this warning the driver needs to release the mutex
> and acquire it again in tpm_dev_async_work() before sending
> the command.

This commit message is nonsense ATM. The code leaves locks held,
which is unacceptable.

Silencing warnings is worst possible rationale for a code change
that I can think of starting from the fact that is straight out
wrong and malicious.

/Jarkko